He arrived in the city on Friday, when he went to a local shooting range where he reportedly learned how to use a gun for the first time.

On Monday, Sandford was denied bail at a district court in Nevada, where he appeared charged with an act of violence on restricted grounds.

Federal Magistrate Judge George Foley declined to release Sandford, who appeared before him in leg irons, over concerns that he was a potential danger to the community and a flight risk.

He will appear in court again on July 5.

A federal public defender told the court that Sandford was autistic yet competent, although he did not enter a plea.

His mother, who has not been named, told the judge he had a history of mental health problems.

According to court research, Sandford did not have permission to be in the US after overstaying a visa and was unemployed. Papers filed at the court said he had been in the country for around 18 months and lived in Hoboken, New Jersey.

He had driven across the US to San Bernardino, California, and had been living out of his car before travelling on to Las Vegas on Thursday.

On Friday, he visited the Battlefield Vegas shooting range where he practised using a 9mm Glock pistol, firing off 20 rounds.

The following day he went to the Treasure Island Casino where Mr Trump was addressing a rally of 1,500 supporters amid tight security.

Attendees had to pass through metal detectors manned by Secret Service, police and casino security officials.

One of those in the crowd, Gregg Donovan, said he had briefly spoken to Sandford while they queued and he seemed "strange".

When he later asked to get an autograph from the billionaire, Sandford allegedly attempted to take a police officer's holstered gun before being tackled and frogmarched from the venue.

A Secret Service report said Sandford told officers he had been planning the assassination for around 12 months and believed he would die in the process.

He had also bought a ticket to a rally in Phoenix, Arizona, for later on Saturday as a back-up.

Sandford was carrying a UK driving licence at the time he was arrested.

A Foreign Office spokesman said: "We are providing assistance following an arrest of a British national in Las Vegas."